This invention relates to calibrating pressure sensors on a tissue examination device.
All women are at risk for breast cancer. This risk increases as a woman ages. Women are generally considered to be at increased risk for developing breast cancer if they have one or more of the following risk factors: a family history of breast cancer, a previous diagnosis of a malignant breast tumor or other gynecological cancers, hormonal factors, or not having had any children or having a first child later in their child bearing years. Even so, the majority of all breast cancers occur in women who apparently do not have identifiable risk factors.
Although breast cancer currently cannot be prevented, it can be detected at an early, treatable stage when the tumor is small and has not spread beyond the breast. Women who are treated at this early stage have a much higher survival rate than women who are treated at more advanced stages of the disease. However, not all breast cancers are currently detected at this early stage. Therefore, the importance of screening for breast cancer has become a critical aspect in the overall management of this disease.
The methods currently used in the United States to screen for breast cancer and other breast conditions include monthly Breast self examination (BSE), mammography, and clinical breast examination.
Breast self examination is manual examination of a woman's breast tissue by the woman herself. During such examinations, a woman should examine her breasts at the same time each month, 7-10 days after the first day of her last menstrual cycle. She should report to her physician anything she feels that is new or that has changed since her prior exam.
Breast self examinations are important for the early detection of breast cancer. However, many women do not perform these examinations. When questioned about this, most women explain that they are not comfortable with their level of skill in doing such examinations. Products which help to remove the obstacles that prevent women from examining their breasts regularly would clearly be beneficial. Ideally, these products would increase the quality of such examinations without requiring extensive technical skill from their users.
Several devices designed to assist the user and clinicians in performing breast self examination are described in commonly-owned U.S. patent application Ser. No. 08/757,466, entitled "Tissue Examination" (hereinafter, the '466 application), incorporated herein by reference. These devices include an array of sensors each of which produces a signal in response to the pressure imposed thereon as the sensor is pressed against tissue. The pressure varies in accordance with properties of different types of underlying tissue structures. Processing tests are performed on the signals to discern the characteristics of underlying tissue structures and thus discriminate between different types of underlying tissue (e.g., potentially foreign structures such as cysts or solid masses, and normal structures such as a nipple, a rib, or a ligament). Accordingly, the devices can alert the user to the presence of suspicious or indeterminate discrete and dominate structures in breast tissue.
Many of the processing tests performed by the devices described in the '466 application search for small differentials in the outputs of the pressure sensors. Random or patterned faults, due e.g. to the sensor state and not the underlying tissue, may produce erroneous test results, thereby potentially leading to "false positive" indications of potentially foreign tissue structures. Moreover, if some of the sensors respond unduly weakly to imposed pressure, the device may fail to detect an underlying structure (particularly if the weakened sensors are concentrated together in the array).